关于expected single matching bean but found 2的问题
问题：
org.springframework.context.support.AbstractApplicationContext refresh
警告: Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userLoginServlet' defined in class path resource [spring.xml]: Unsatisfied dependency expressed through bean property 'userDao'; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'cn.tedu.spring.UserDao' available: expected single matching bean but found 2: userDao,subUserDao
Exception in thread "main" org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userLoginServlet' defined in class path resource [spring.xml]: Unsatisfied dependency expressed through bean property 'userDao'; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'cn.tedu.spring.UserDao' available: expected single matching bean but found 2: userDao,subUserDao
***——>Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'cn.tedu.spring.UserDao' available: expected single matching bean but found 2: userDao,subUserDao
分析：使用了根据类型(byType)的自动装配方式，这种自动装配要求最多只有1个匹配类型的对象，但是，在Spring容器中却出现了2个这样的对象，Spring就不知道应该装配哪一个了，就会出现错误！
解决方案：使得Spring只管理其中1个类型的对象，或者，使用byName方式来装配。
异常：NoUniqueBeanDefinitionException：不唯一的Bean匹配异常